That means they can vote with their conscience rather than following the orders of party managers - an unusual move for a vote on a major policy, with Labour saying it showed she had "given up any pretence of leading the country".

The PM had made a last minute plea to MPs to back her deal after she had secured legal assurances on the Irish backstop from the EU.

But although she managed to convince about 40 Tory MPs to change their mind, it was not nearly enough to overturn the historic 230 vote defeat she suffered in January, throwing her Brexit strategy into fresh disarray.

Please upgrade your browser to view this interactive

Did your MP vote for or against the provisional Brexit deal?

Enter a postcode, or the name or constituency of your MP

Seat vacant

In a statement after the defeat, Mrs May said: "I continue to believe that by far the best outcome is the UK leaves the European Union in an orderly fashion with a deal.

"And that the deal we have negotiated is the best and indeed only deal available."

Setting out the next steps, she said MPs will vote on Wednesday on whether the UK should leave the EU without a deal or not.

If they vote against a no-deal Brexit, they will vote the following day on whether Article 50 - the legal mechanism taking the UK out of the EU on 29 March - should be extended.

Mrs May said MPs would have to decide whether they want to delay Brexit, hold another referendum, or whether they "want to leave with a deal but not this deal".

She said that the choices facing the UK were "unenviable", but because of the rejection of her deal, "they are choices that must be faced".

Labour leader Jeremy Corbyn said the prime minister should now call a general election.

"The government has been defeated again by an enormous majority and it must accept its deal is clearly dead and does not have the support of this House," he told MPs.

He said a no-deal Brexit had to be "taken off the table" - and Labour would continue to push its alternative Brexit proposals. He did not mention the party's commitment to back another referendum.

Jacob Rees-Mogg, chairman of the European Research Group of Brexiteer MPs, said "the problem with the deal was that it didn't deliver on the commitment to leave the EU cleanly and that the backstop would have kept us in the customs union and de facto in the single market".

Media playback is unsupported on your device

Media captionChris Mason: "A huge defeat for the tweaked Brexit deal"

The Tory MP, who voted against Mrs May's deal, told BBC News: "The moral authority of 17.4 million people who voted to leave means that very few people are actually standing up and saying they want to reverse Brexit. They're calling for a second referendum, they're calling for delay.

"But actually very few politicians are brave enough to go out and say they want to overturn the referendum result."

Leading Conservative Remainer Dominic Grieve, who backs another referendum, said Mrs May's deal was now "finished".

The Tory MP, who voted against the prime minister's plan, said he was confident the majority of MPs would now vote against a no-deal Brexit - and he hoped they would then vote to ask for an extension to Article 50.

Media playback is unsupported on your device

Media captionCorbyn: PM's Brexit plan "is dead"

The EU's chief Brexit negotiator Michel Barnier said in a tweet: "The EU has done everything it can to help get the Withdrawal Agreement over the line. The impasse can only be solved in the UK. Our 'no-deal' preparations are now more important than ever before."